This invention relates to a vacuum lifting/lowering head, e.g. for use in conjunction with vacuum lifting apparatus, such as the general kind described in GB 2080764. The invention also includes said vacuum lifting flowering in combination head with such a vacuum lifting apparatus.
With such apparatus the expansion or contraction of the variable length, bellows-like lift tube is controlled by controlling the vacuum level within the tube, which level is in turn controlled by a user operable, or settable, valve to connect and/or isolate the interior of said lift take to atmosphere. Thus, in a fully open valve position, the tube interior is open to atmosphere, the vacuum within the tube is rapidly destroyed and, with the tube hanging vertically from a suspension point, the tube falls to its maximum expanded length. Conversely, in a fully closed valve position, the vacuum is at a maximum and the tube rises to its maximum contracted position--being in use a maximum lift height. It follows that intermediate opening of the valve achieves an intermediate position.
Previously proposals for valve arrangements for vacuum lifting/lowering heads have however been relatively complex and hence costly c.f. GB 2080764 and 2200615, and the object of the present invention is to provide a head of simple operation and hence of low manufacturing costs.